Process for manufacture of acetylenic alcohols



June 6, 1961 J. HAPPEI. ETAL PROCESS FOR MANUFACTURE OF' ACETYLENICALCOHOLS Original Filed Aug. 1l, 1955 ZODAOm I9: l'

trum Ik@ OF 10k mDOtQ IZ mT tOhO t All om: m21 mrw a vom N5 s om mmsKNHS: QmvGOtnI IO! Qmhm'jml a LWL- John Happel im Charles J. Morse!lnvenors Attorney United States Patent O 1 Claim. (Cl. 26o-63s) Thisinvention is concerned generally with a continuous and commerciallypractical process for the production of acetylenic hydrocarbons by aseries of interrelated and coacting steps, and more specifically, with aparticularly useful method for the manufacture of 2-methyl1,5hexadiene-S-yne.

It has been previously known to produce various hydrocarbons havingunsaturated bonds, including both double and triple fbonds, by thermalpyrolysis. This drastic technique is only applicable to the lesscomplicated types of hydrocarbon structures. For instance, methylacetylene has previously been made by the thermal pyrolysis method, butonly in relatively low yields. However, it is substantially impossibleto produce complicated molecular structures having a multiplicity ofdouble and triple bonds by this method.

Organic compounds having both acetylenic bonds and olenic double bondsgive especial diiculty in their production even on laboratory and smallbatch type operations. Various diticulties are encountered in theapplication of the known methods, including the degradation anddecomposition reactions of both the starting materials as well as theacetylenic olen hydrocarbon products. Such `byproducts and sidereactions result in both loss in yield of product as well as loss of therelatively expensive starting material.

The present invention is concer-ned with improved means for producingacetylenic alcohols and includes irnprovements in addition to thosedescribed in copending application U.S. Serial No. 384,846, filedOctober 8, 1953, now abandoned, of which the instant application is acontinuation-in-part. This invention is more particularly concerned withthe production of the acetylenic alcohols and employs valuableimprovements in the condensation step between the acetylenic hydrocarbonwith the carbonyl compound.

This application is a divisional application of U.S. Serial No. 527,828,tiled August 11, 1955, now U.S. Patent 2,922,765, issued January 26,1960.

Certain of the organic compounds of the class of the alkyl olefinicacetylenes, especially 2-methyl-1,5hexa diene-B-yne, may be prepared bythe process of this invention. This class of compounds contains both theacetylenic bond and multiple oleiinic bonds, and consequently gives theabove described diiiculties in their preparation by previously knownmethods.

In general, the invention involves a method for synthesizing acetylenichydrocarbons by the combination of carbonyl compounds which may beeither aldehydes or ketones with either acetylene or acetylenichydrocarbons in which caustic alkali is the most frequently usedlcatalyst. The acetylenic alcohol produced as a result of this reactioncan, if desired, thereafter be converted to an acetylenic oletinhydrocarbon by a dehydration. The whole series of steps is carried outin a practical manner on a continuous scale Without the usual hazardswhich are often encountered in this type of operation.

Although in the previous art, the use of suspensions of solid potassiumhydroxide has been generally disclosed,

it has been found that the preparation of Such suspenice sions in astable, usable form involves considerable diiculty and embraces novelfeatures not previously known or disclosed. Although simple suspensionsmay be reasonably satisfactory when the condensation reaction isconducted in an agitated batch vessel, they give completelyunsatisfactory results when they are of necessity, made up at a periodof time previous to the reaction, and then used as feed to a continuousreactor.

Many techniques were attempted in an etort to prepare stable potassiumhydroxide suspensions and particularly using xylene as the suspensionliquid. F or instance, attempts were made using liquids other thanXylene. These included alkyl acetals and polyethers. The use of Carbitol(diethylene glycol monoethyl ether) was studied. Dibutyl acetal was alsoemployed without success in attempts to prepare stable suspensions.Further, attempts Were made also to employ various so-calledsolubilizers such as mercaptans and phenols in preparing aqueoussolutions containing a high percentage of potassium hydroxide. Anothertechnique studied was that molten potassium hydroxide was sprayed intothe reaction chamber and as the hydroxide particles solidified, a tinesuspension was obtained. The use of alcoholates was also investigated.Generally, diiliculties are encountered in the preparation of thealcoholates or acetal. The alcoholates were made by reacting potassiummetal with the appropriate alcohol. An attempt was also made to producethe alcoholates by reacting the alcohol with potassium hydroxide, andthereafter removing the water of reaction by distillation. This reactionwas successful only with cresol, but this reagent did not producecondensation. None of the above schemes and methods were successful foruse in continuous processes in which this reagent is used.

It was discovered quite surprisingly that solid potassium hydroxideparticles can be suspended by the use of a relatively smallproportion-of certain fatty acid salts of the alkalis. Using criticalconditions of procedure, as will be described more particularly below,this technique yields unexpectedly and unusually stable suspensions ofsolid potassium hydroxide in hydrocarbon diluents or solvents, such asxylene and the like. Such suspensions so formed are outstandingly suitedfor use in continuous processes involving the condensation reactions.

In order to determine the various materials which can be satisfactorilyused in preparing the stable slurries, a number of comparativeexperiments were made. In each instance the same procedure was employed.50 parts of xylene and 25 parts of potassium hydroxide were heatedtogether to about C. Under these conditions, 1/z part of oleic acidproduced a stable emulsion which upon cooling resulted in a stableslurry of finely divided potassium hydroxide suspended in x-ylene. TableI below lists some of the other materials which were tested.

1A mixed fatty acid `r'ossiu ester made by condensing 15 moles ethyleneoxide per mole of an acid mixture. The acid mixture consists of 70%ahietic acid and the remainder, a. mixture of oleic and linoleic acids.

2 Acetate salt of a diamine made by condensing acrylonitrile with aprimary amine made from tallow.

This process is especially applicable'to the preparation of the2alkyl1,5-hexadiene-3-ynes in which the alkyl group has from l to 5carbon atoms. Although the process will be described in greater detailusing as initial reactants, vinyl acetylene and acetone, other ketonessuch as methyl ethyl ketone or methyl vinyl ketone as well as aldehydesmay also be employed. In addition, other alkyl oletinic acetylenichydrocarbons can be prepared by starting with other acetylenic compoundssuch as methyl acetylene, or diacetylene, and condensing with theappropriate ketone. It isl desirable but not essential to use ketonessince the dehydration step of the over-all process is well adapted tothe dehydration of the tertiary alcohols produced by the condensation ofketone type compounds.

When employing reactants and materials of a hazardous nature such asacetlyene and especially some of the more reactive hydrocarbons whichhave additional double and triple bonds, it is obvious that a continuousprocess possesses substantial advantages. The amount of materialshandled at any one time can be kept small enough so that in the event ofan explosion or other mishap, no extensive damage will result.Furthermore, the operating conditions can be continuously and carefullyregulated to avoid substantially completely undesirable polymerizationreactions, while at the same time maintaining conditions for optimumyields of the desired condensation products. In fact, substantialcommercial production of materials of this chemical type is practicallyimpossible unless continuous production can be successfully ernJ ployed.

The general process of the invention may be described Yas follows,allowing for suitable variations in the operation. A slurry of potassiumhydroxide in xylene is rst made up in an agitated reactor vessel usingthe special and highly advantageous procedure which is further describedhereinbelow.

With regard to making the slurry of potassium hydroxide, the temperatureemployed at atmospheric pressure can vary from about 140 C.(approximately the boiling point of xylene) down to approximately 5 C.below which temperature the slurry tends to become gelatinous and istherefore more diiicult to handle. At higher pressures, highertemperatures can be employed. Lower temperatures are useful provided arelatively higher proportion of xylene is employed. The concentrationsof fatty acid, for example, oleic acid, which may be employed vary fromabout V2 to 5% by weight, with the preferred amount Vbeing about 1% byweight. Higher concentrations are to be avoided because a very viscousslurry results. The preferred proportions of potassium hydroxide indiluent is approximately one part by weight of potassium hydroxide pertwo parts by weight of xylene. Concentrations as high as 1 to 1 havebeen employed but such proportions yield more concentrated slurrieswhich are more diicult to handle and pump in the equipment.

A solution of an appropriate acetylenic hydrocarbon (vinyl acetylene)mixed with an appropriate carbonyl compound such as an aldehyde orketone (acetone) is kept in storage in a'separate feed tank. The slurryof potassium hydroxide and the mixture of acetylenic hydrocarbon andcarbonyl compound are fed into the recirculating portion of acondensation reaction system at different points. If desired, it is alsofeasible and possible to -feed the acetylenic hydrocarbon reactant andthe carbonyl compoundreactant separately into the condensation system.Thus, there may be provided a n`rstrecirculating sysmately 20% of thereaction volume is in the recirculating section and 80% is in thenon-recirculating section.

The resulting reaction mixture lfrom the condensation reaction vessel isthen brought into contact with water in order to hydrolize the potassiumsalt of the acetlyenic alcohol which is produced. Both the aqueous andorganic phases are contacted in a tower which is provided with means tosecure intimate mixing, as for example, a perforated plate column.Contact in this column is preferably countercurrent. The overhead orupper fraction from the hydrolysis column is then separated into anorganic phase and an aqueous phase and each is collected separately. Theacetylenic alcohol from the condensation is contained in the xylenelayer from which it may be separated by distillation, if desired.

Depending on the boiling point of the alcohol produced by thecondensation, other hydrocarbons than xylene may be employed as diluentsin the reaction in order to facilitate separation of the product bydistillation if this is desirable. In some cases, as when furtheremploying the alcohol as a chemical intermediate, it is preferable notto separate it from the diluent hydrocarbon in which it was produced.

On the other hand, the hydrocarbon-alcohol layer can be mixed with asolution of suitably controlled dilute sulfuric acid and this mixture isagain continuously passed through a dehydrating zone such as a countercurrent contacting column at an elevated, controlled temperature duringwhich period the alcohol from the condensation is dehydrated to thehydrocarbon. The mixture leaving this zone separates into two layers, anaqueous layer and a hydrocarbon layer. The hydrocarbon layer is thenpreferably subjected to a fractional distillation for the removal of thedesired acetylenic olenic hydrocarbon (Z-methyl- 1,5-hexadiene-3-yne)preferably as an overhead product.

The choice of operating temperatures is not only governed by theproperties of the postassium hydroxide slurry but also by the particularcondensation reaction which it is desired to carry out. Higher reactiontemperatures further the condensation reaction, but also favorpolymerization of the acetylenic hydrocarbon reactants. Thesehydrocarbons vary a great deal in degree of stability. For example, thecondensation of acetone and vinyl acetylene can be conducted effectivelyat temperatures ranging from 2O to 40 C. without excessive side reactionpolymerizations. Condensations involving such hydrocarbons asdiacetylene can best be effected at 0 to 10 C. or lower. The normallygaseous acetylenic hydrocarbons such `as acetylene or methyl acetylenerequire slight modifications of the continuous procedure. Methylacetylene is quite stable at high temperatures so that the preferredoperation is at 20 tov 30 C. with sucient pressure being maintained sothat the methyl acetylene dissolves in the ketones or aldehyde withwhich it is being condensed. ln some cases, it is more desirable toconduct the operation in two steps whereby the acetylene is Ylirst'reacted with the potassium hydroxide slurry to form the correspondingpotassium acetylide, which then in turn is reacted with the desiredketone or aldehyde. Since .aldehydes Vare generally more sensitive toelevated temperatures than are ketones, lower temperatures are usual-Yly to be preferred incondensation reactions involving 'aldehydes asreactants.

A number of unique and inventive features are embodied in thiscontinuous method of operation. The continuous condensation oftheacetylene compound and the carbonyl compound in the presence of thepotassium hydroxide slurry is `possible because of the discovery thatthe reaction takes place relatively rapidly under these conditions. Theemployment of a continuous reactor system has the advantage that thehazards usually associated with handling large quantities of theexplosive and dangerous acetylenic compounds are much reduced andeliminated. The immediate and direct continuous dehydrationV of theacetylene condensationY product with controlled amounts of sulfuric acidalso has the advantage of minimizing the hold-up of unstable materialand thereby avoiding substantial losses in yield of desired material. Itis further highly desirable to etect condensation, and, if desired, thedehydration of the resulting alcohol condensation product, in thepresence of a relatively high boiling hydrocarbon diluent. The diluentshould be selected such that it does not interfere with the entirecondensation and dehydration reactions. The preferred hydrocarbondiluent for this purpose is xylene. The xylene which may be used can beeither one of .the pure isomers or a mixture of two or more of theisomers such as is readily available commercially. The employment of adiluent such as xylene throughout the process has the advantage ofmaintaining a solvent in the presence of the usually unstable acetylenicpolymers, which otherwise are quite explosive and present hazards whenemployed in the pure state. In carrying out this continuous operation,the xylene concentration is maintained throughout the reactor, thedehydrator and in the iinal distillation steps during which elevatedstill temperatures may be experienced and would otherwise causeexcessive polymerization if the xylene were not present. This xylenewere not present. This xylene or other suitable xylene or other suitablesolvent may be recycled and reused throughout the continuous reactorsystem. If desited, the potassium hydroxide as well as the aciddehydrating agent may also'be recycled.

lThe following examples are intended to be for the purpose ofillustration only and it is not intended in any way to limit theinvention to the specific embodiments shown therein. All parts are byweight unless otherwise specified.

Example 1 ln a typical specific application of the above describedprocess the preparation of 2-methyl-5-hexene-3-yne-2-ol was carried outby the condensation of acetone with vinyl acetylene.

The continuous condensation was carried out in an apparatus similar tothat described below and sketched in the accompanying schematic flowdiagram. A slurry of potassium hydroxide was made up in a blendingapparatus using 80 parts of potassium hydroxide, 160 pants of xylene andabout 2 parts of commercial oleic acid. The xylene-potassium hydroxidemixture was heated to about 140 C. (above the melting point of thepotassium hydroxide), and the oleic acid was added. The mixtureimmediately formed an emulsion which was -agitated while undergoingcooling to 25 C. As the mixture cooled, the potassium hydroxidesolidified so that a suspensoid systern consisting of solid potassiumhydroxide particles suspended in xylene resulted. Using this procedure aslurry was obtained which was yfound to be entirely stable at roomtemperatures (with occasional slight agitation) for periods up -toseveral months. The total volume of the reaction system employedincluded both the recirculating and non-recirculating portion. TheIabove described slurry and vinyl acetylene-acetone mixture were eachfed into the system at a rate corresponding to l part by volume perminute. Equimolar quantities of vinyl acetylene and acetone (0.855 moleof each) were used. The recirculating portion of the system operated -at35 to 40 C. and the non-recirculating portion was maintained at slightlyabove room temperature at 25 C. The resulting reaction product washydrolized with 75 parts of concentrated sulfuric acid and there wasobtained a yield of 2-methyl-5-hexene-3-yne-Z-ol equivalent to 74% ofthe theoretical quantity.

Example 2 A stable slurry of potassium hydroxide was made up in asimilar fashion as that described in Example 1 above, said slurrycomprising 80 parts of potassium hydroxide (1.43 moles), and 160 partsof xylene and employing 2 parts of oleic acid as emulsifying agent.Ilnto this stable suspension there was -absorbed 0.924 mole (24 parts)of acetylene by slowly passing acetylene into a recirculating systemcomprising 20 parts by volume. 'I'he system was maintained at a.temperature of approximately 35 to 40 C. Subsequently, this suspensionwas passed into a second recirculating system into which an equivalentquantity of butyraldehyde was introduced, that is, 0.92 mole. Followingthis introduction, the mixture was passed into a non-recirculatingchamber comprising 77 parts by volume. The resulting reaction productwas hydrolyzed to obtain a good yield of l-hexyne-B-ol.

Example 3 The following example will best be understood if it is read inconnection with the accompanying gure which is a schematic ow planpresented for the purpose of illustrating the process of the invention,although it is not intended to -limit the invention speciiicallythereto.

The potassium hydroxide-xylene mixture is made up in vessel A which is areactor, the contents of which are continuously agitated by stirrer 2.The make up xylene is introduced into vessel A by line 11 and pelletedpotassium hydroxide is introduced by line 3. The slurry is prepared bycontinuously mixing the reactants at a temperature of about C. withrapid agitation. After a suitable period of time, in reactor vessel A,the resulting iinely divided KOH-xylene slurry is passed by line 4through inlet line 5 into the condensation reaction system B. Thissystem consists of two sections, one recirculating and the othernon-recirculating. The KOH-xylene slurry is fed into the recirculatingsection of the reaction system; the circulation being maintained bymeans of pump 6. The acetylenic hydrocarbon (vinyl acetylene) and theketone (acetone) in the xylene diluent, are simultaneously introducedinto the recirculating section via line 7. The desired reactiontemperature (about 40 C.) is maintained by controlling the coolant flowthrough an appropriate heat exchanger. The mixed reactants then passthrough the non-recirculating section 9 where the condensation reaction'between the acetylenic hydrocarbon (vinyl acetylene) and the ketone(acetone) is allowed to go to completion. Any ixed gases in the systemare Vented through trap 8.

The reaction mixture is then brought into contact with water which isfed through line 10. This water dissolves the unused KOH and alsohydrolyzes the potassium acetylide complexes. Complete hydrolysis isaccomplished by contacting the aqueous and organic phases in the packedhydrolysis column C. The total mixture is then passed (after hydrolysis)by line 12 into separator D.

The organic layer containing unreacted vinyl acetylene, xylene, anddesired condensation product passes via line 14 into dehydration reactorF. There is also introduced dilute sulfuric acid (about 30%) whichenters the system 'by line 15. The aqueous layer from separator D issubsequently processed as described below. In dehydration reactor F, thecondensation product is subjected to an elevated temperature whereby itis continuously dehydrated to the acetylenic olefin hydrocarbon. Thisdehydrated product passes by line 21 into phase separator H in which thegas phase which is principally unreacted acetylenic hydrocarbon isseparated and passed via recycle line 23 into line 5 and thence into thecondensation reaction system B. The organic layer obtained in separatorH is drawn oi by line 22 and thence is passed into an acid `recoverysystem, if desired.

In washer I, the organic layer containing the desired acetylenic olenhydrocarbon product, undehydrated alcohol, and xylene is contacted withwater introduced by line 24. Wash water is removed from the washer byline 25. The washed organic layer is then passed by line 26 intofractionating column I, wherein it is subjected to fractionaldistillation. Fractionating column I is preferably operated underreduced pressure. The desired hydrocarbon,Y2-rnethyl-1,5-heXadiene-3-yne, is removed from this column by overheadline 33. This overhead stream passes through a condenser. A part of thecondensed liquid is returned to the column as reux via line 34. Theremainder is removed as product by line 35. From the lower portion offractionation column I, a major portion of the bottoms stream ofundehydrated alcohol and Xylene is recycled through line 20 into line 14and thence into dehydrator F. A smaller portion of the bottoms streampasses by line 27 into rerun column K. In this column, the Xylenediluent is continuously puried by removal of a polymer bottoms streamthrough line 28. The Xylene is removed overhead from column K by line 29and passes through a condenser. A part is returned to column K by line30 and the remaining portion passes through line 31 and is recycled4back to the condensation and dehydration stages. Polymerizationinhibitor can be added to the system by line 32, if desired.

The aqueous KOH layer containing some dissolved organic material ispassed through line 13 t0 extraction tower E, in which the layeriscontacted countercurrently Iwith fresh Xylene introduced via line 17.The enriched xylene is passed through lines 16 and 20 and 8y thence intoline 14 to the dehydration reactor F. The stripped aqueous KOH solutionis passed to vaporizer F in which water is removed by azeotropicdistillation with Xylene to obtain anhydrous KOH which is removed byline 19 and which can be used in making up the initial slurry in vesselA.

What is claimed is:

A continuous process for the production of 2-methyl- S-hexene-3-yne-2-olwhich comprises continuously dispersing solid potassium hydroxide inXylene in the presence of from 1/2 to 5% by Weight of oleic acid,continuously contacting said dispersion with vinyl acetylene and acetonein the presence of xylene, and hydrolyzing the resulting product toproduce 2-methyl-5-hexene-3-yne- 2-01.

References Cited in the le of this patent UNITED STATES PATENTS2,394,608 Hansley Feb. 12, 1946 2,455,058 Herman Nov. 30, 1948 2,536,028Brothman et al Jan. 2, 1951 2,579,257 Hansley et al. Dec. 1S, 19512,596,175 Rosenstein May 13, 1952 2,742,517 Fusco Apr. 17, 1956

